Automatic grid machine



.Aug` 8, 1961 s. J. GARTNER ET AL 2,995,156

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Aug. 8, 1961 s. J. GARTNER ET AL l 2,995,156

AUTOMATIC GRID MACHINE Original Filed Sept. 3. 1947 5 Sheets-Sheet 4Aug- 8, 1961 s. J. GARTNER ET AL 2,995,156

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United Stat Patent AOfce l Patented Aug. v8, 1961 .Continuation of`application Ser. No. 771,996, Sept. 3,

'1947. This application May 2.1, 1958, Ser. No. 736,925

42 Claims. (Cl. Mtl-71.5)

This invention relates to machines for making grids for electrondischarge devices and the like and to feeding, `stretching and severingdevices for like machines. This 1s a continuation of application SerialNo. 771,996, led September 3, 1947, entitled, Automatic Grid Machine.

In a companion application iiled concurrently herewith by Stanley J.Gartner, a novel machine for forming a strip of grids in a continuousand automatic fashion is described, with principal emphasis on theforming end of the machine. The form of grid involved includes one ormore side rods to which multiple spaced turns of line wire are secured.The feeding of the grid strip during its formation, accomplished bydrawing the side rods past forming devices, should be uniform andreliable to the end that the helical turns of tine wire may beaccurately spaced in accordance with design specifications.

It has become accepted practice to stretch the side rods of formedstrips of grids, either cold or hot, in order that `the grids may beuniform and straight when completed.

It is also necessary to divide strips into individual grids. Theseoperations are commonly effected as separate operations, in adiscontinuous procedure, following the forming of a strip of grids.

Accordingly it is the principal object of this invention to provide anovel grid-making machine having devices to enable grid strips to beformed very accurately, and to be processed into completed grids in acontinuous manner in the forming machine. It will be apparent as thedescription proceeds that the various features of the illustrativemachine described herein may be employed according to my inventionwithout others of the features, but when integrated into a singlemachine, especially with the grid-forming devices in the above companionapplication, a grid-making machine of notable characteristics isobtained.

In usual machines the grid lateral is helically wound about the siderods at a constant rate. As a result the spacing between the helicalturns is determined by the rate of side-rod feed. Usually the turns of agrid are to be uniformly spaced and the side rods are drawn past theforming devices at a uniform rate. It is nevertheless advisable toadvance the side rods very rapidly at the endV of each grid-windingcycle so that the number of gridlateral turns left unsecured, betweenthe wound and secured grid laterals, may be held to a minimum to limitthe amount of unsecured grid-lateral wire that is waste. Furthermore itis often necessary to vary the mutual spacing between the secured turnsand to accelerate the feed during winding of the widely-spaced looseturns. Accordingly a specific object of the present invention is todevise a feeding mechanism that can be made to cyclically vary the rateof feed of grid side rods according to an arbitrary schedule. A furtherobject in this connection is to provide such feed mechanism in the gridmachine that the organization is readily susceptible to change formanufacturing grids of different length and diiferent grid-lateraldistribution and spacing.

Another feature of the improved grid machine is the incorporation of anautomatic stretching arrangement to straighten the grid side rodswithout disturbing the continuous cyclic operation. Still anotherfeature is the incorporation of a severing device to divide the stripinto separate grids, and to remove the side-rod material deformed by thegripping faces in the feeding and stretching heads. A further feature isconcerned with novel feedjaw construction for reliably engaging the gridstrip, without disturbing the feed rate as would be occasioned byelongation of the strip incidental to ordinary deformation by the feedjaw.

The invention will be better understood from the following specificdescription of an illustrative embodiment of the invention shown in theattached drawings wherein:

FIG. 1 is a plan view of the preferred embodiment with certain partsbroken away and others omitted for clarity.

FIG. 1A is the elevation of an operating cam and hydraulic valve detail.

FIG. 2 is an elevation of the structure in FIG. 1 with parts lbrokenaway and omitted for clarity, showing a wiring detail in addition.

FIG. 3 is a longitudinal sectional detail of the mechanism forstretching the side rods.

FIG. 4 is an elevation of the second feed head and operating mechanism,being illustrative of the` threeother four-motion heads in the machine.

FIG. 5 is a plan view of a portion of the mechanism in FIG. 4.

FIGS. 6 and 7 are alternative forms of grid that .can be made with theillustrative machine.

FIG. 8 is a diagram of the hydraulic system for operating variousmechanisms in the presently preferred machine.

FIG. 9 is an elevation of the feed jaws of the second feed head, beingillustrative of the jaws in the first feed head and the stretch head.

FIG. lO is a fragmentary sectional view of the feed jaws along the line10--16 in FIG. 9.

FIGS. 11 and 12 are enlarged sectional detail views of successive feedjaws according to alternative embodiments.

FIG. 13 is a cam chart, corresponding closely vto a timing chart of theimportant' operations in the improved grid machine. v

GENERAL Referring now to FIGS. l and 2 the side rods R are drawn to theright by the feed mechanism, to be described, through guide tube 10 andlaterally supported by mandrel 12 iixed to the end of tube 10.Grid-lateral wire L from reel 14 is directed by guide 16 to the exactpoint along mandrel 12 where the grid lateral is to be laid. Reel 14 andguide 16 form part of Winding head 18 that is rotated about tube 10.

A pair of sharp-edged notehing discs 20 are reciprocable in alternationagainst rods R on mandrel 12 and in ad- Vance of the point where guide16 lays grid lateral L. A pair of blunt-edged peem'ng discs 22 are alsoreciprocable against mandrel 12, in alternation with each other and inalternation with the adjacent notching disc, to secure the grid-lateralwires in place immediately after they are wound by guide 16 on head 18.Rods R are gradually drawn to the night while the notching, winding andgridlateral-securing operations take place to form a series of securedturns of grid lateral wire on side rods R, either evenly spaced orunevenly spaced as in the completed grids of FIGS. 6 and 7. At thecompletion of each sequence of secured turns, the contact between discs20 and 22 with side rods R is interrupted while the winding ofgrid-lateral wire continues. During this time the side rods R yareadvanced to the right more rapidly than usual and several loose turns ofgrid lateral L are wound. The winding of the loose turns is for thepurpose of maintaining continuity of grid lateral L between the sequenceof secured turns that are to form the grid in FIGS. 6 and 7, duringthose intervals when side rods R are drawn past the grid-forming deviceswithout having grid-lateral wire attached, The rapid side-rod feedprovides the necessary lengths of side-rod material for grid terminalsand locating extensions, and fordeform-ation incidental to the feedingoperations.

A pair of blades 24 and 26 (FIG. 1) and a mechanical picker 27 (FIG. 2)are jointly effective to separate the loose turns from the secured turnsand to remove the separated turns from the machine. As a result theuncompleted strip G` of grids is drawn to the right beyond the gridforming tools, having groups of secured turns spaced by lenths of bareside-rod wire R.

The devices described to this point are more fully disclosed in U.S.Patent No. 2,759,499 of August 2l, 1956, assigned to the assignee of thepresent invention.

The strip of grid material G is continuously drawn through the machineby a pair of feeding heads 28 and 30 each of which operates in 'afour-motion path to grip the material, draw it along the machine,release it, and return for a renewed feeding stroke. The timing of thefour-motion strokes is such that there is continuous feeding through themachine without a disturbance such as would otherwise cause erraticspacing of the grid-lateral turns. An additional head 32 is provided forstretching the side rods and, optionally, for heating them electricallyduring the stretching operation. A fourth head 34 divides the grids fromeach other to yield individual grids, and to cut out the portions ofside-rod material that have been deformed by the feeding and stretchingheads.

The first feeding head 28 fis carried by bracket 36 on shaft 38 which isaxially reciprocated parallel to the travel of grid strip G andcompletes one cycle of reciprocation for each completed grid. Cuttinghead 34 is also secured to shaft 38 by bracket 49. A second shaft 42,parallel to but laterally spaced from shaft 38, carries bracket 44 forsupporting the second feed head 3G. Stretching head 32 is carried onhead 30 by a pair of threaded shafts 46 and 48, but is cyclicallymovable along the strip of grids in relation to head 30 by hydraulicpistons described below.

Each shaft 38 and 42 is axially reciprocable by cam mechanism foreffecting longitudinal movements of the several heads 28, 30, 32 and 34parallel to the travel of the grid strip and in the restoring direction.Hydraulic actuators are used for effecting gripping and separatingmotions of the maws within the several heads. Hydraulic cylinders S0, 52and 54 for this purpose are shown in FIG. 2. The axially reciprocatedshafts and the hydraulic actuators are timed to close the jaws of thehead of the grid strip, move with the strip, separate and then return,in a four-motion path.

Head travel The mechanism to operate shafts 38 and 42 axially for movingthe feeding, stretching and cut-ting heads parallel to the grid-stripwill now be described. Shaft 38 is supported in a pair of bearings 56and 58 which are secured to the bed plate 60 of the machine. Shaft 42 issimilarly carried by bed plate 60 in bearings 58 and 62. At the rightextremes of shafts 38 and 42 are a pair of fixed abutment rods 64 and 66having enlarged ends as 68 on -rod 64 (FIG. 2) which is s'lidable in thebored end of shaft 38. A spring 70 acts between the end of the bore inshaft 38 and enlargement 68 yto urge shaft 38 constantly to the left. Asimilar enlarged end, bore and spring construction urges shaft 42constantly to the left. Shaft 38 carries cam follower 72, maintained incontact with cam 74 by spring 70. Cam follower 72 is adjustable alongshaft 38 by means of capstan nut 76, threaded and shouldered rod 78, andabutment Sil which is xed to shaft 38. By rotating nut 76 when cam 74 isstationary it is possible to adjust the position of the first feedinghead 28 and of cutting head 34 along the grid strip. By Virtue of theseadjustments the feeding heads can be caused to engage grid strip Gaccurately between the lengths of side rods R to which the grid lateralL is secured, and each of the heads can be made to register with thedeformation formed by the preceding head. Cutting head 34 can beadjusted relative to iirst feeding head 28 by loosening the bracket bywhich it is carried on shaft 38. Cam follower 82 on cam 74, spaced 180from cam follower 72, is adjustably carried by shaft 42 and reciprocatesheads 30 and 32 along the grid strip.

Cam 74 is rotated -by cam shaft 84 which is supported in split bearing86, 88 depending from bed plate 60. Shaft 84 is rotated once for eachcomplete grid cycle by gear 90 driven in turn by pinion 92 on driveshaft 94.

At its left extreme, shaft 84 carries a cam follower 96 which-is heldagainst rotation with that shaft by an arm 9S, and -is provided with athrust bearing. Arm 95 is slidable in fixed grooved plate 97. Camfollower 96 is urged against cam 98Vby the same springs, as '70, thatmaintain cam followers 72 and 82 against cam 74. Cam 98 on shaft 108 iisdriven from shaft 94 through spiral gears 102 and 104 :to reciprocateshaft 84 axially once each grid cycle. Shaft and gear 102 are carried inhousing 106 supported from bed plate 60.

Operation of jaws in heads Before considering the effect of cams 74 and98 on the various feeding, stretching and cutoff heads, the nature of anindividual head will first be described. For this purpose the secondfeeding head 3) shown in FIG. 4 is taken as typical. The other headshave the same type of operating linkage and frame construction, althoughframe detaiis are varied among the heads in order to meet spacerequirements.

Second feeding head 30 is supported on shaft 42 by bracket 44 includingclamping portion 44a. This head comprises a frame 168 having a groovedface-portion 110 for laterally guiding a pair of slides 112 and 114carrying the maws to grip the strip of grid material G. A pair of gibs116 and 118 are secured to frame 108 to guide and retain slides 112 and114 against face-portion 110.

Slides 112 and 114 have similar operating linkages, and are reciprocatedtoward and away from each other by a common hydraulic actuator.Hydraulic fluid is alternately admitted to lines 120 and 122 supplyingcylinder 52 for reciprocating piston 124. This reciprocatory drive istransmitted to connector 126 by link 128 to operate a pair of bellcranks 130 and 132 which are pivoted on frame 108. The operative strokeof connector 126 is transmitted through these bell cranks to links 134and 136 respectively which are secured by eccentrics 138 and 140 toslides 112 and 114. The eccentrics can be locked in any adjustedposition in a suitable manner.

The strokes of jaws 112 and 114 are enforced cyclically by hydraulicpressure, being limited by the excursion of piston 124 in cylinder 52.The ultimate positions of slides 112 and 114 in engagement with gridstrip G are determined by adjustment of eccentrics 138 and 140 and byfixing the length of connector 126 at adjustable portion 142.

The second feeding head 3i) differs notably from the first head 28 andfourth head 34 in that it supports a pair of cylinders and pistons forsupporting and operating the third or stretching head 32. In addition,because of the long space between shaft 42 which supports head 30 andthe center of mass of the head, a plate 144 is provided on head 3ft forsliding in guide 146 carried by arm 148 rigidly secured to bed plate 60.Heads 30 and 32 are guarded by this plate and guide construction againstpivoting downward about shaft 42.

Stretching head The mechanism for operating stretching head 32 is bestshown in FIGS. 3, 4 and 5. The stretching of grid strip G is to beeffected while the side rods are cold tion as shown.

or, opitonally, while the siderods are electrically heated. For thispurpose the heads are electrically insulated apart, as will appear, anda voltage applied between the heads is impressed on the strip.

In FIG. 3 cylinder 150 is shown supported in frame 108 and carrying apiston 152 at the left end of rod 46. Frame 108 of stretching head 32 isadjustably secured to threaded shaft 46. When hydraulic iluid isadmitted to cylinder 150, the stroke of piston 152 carries stretchinghead 32 away from the second feed head 30 at a time when the jaws of`both heads 30 and 32 are closed on grid strip G. Second feeding head 30actually travels along bed plate 60 in drawing the grid strip past theforming devices including the forming head; but piston v152 moves head32 faster in the feeding direction and `stretches the portion of gridstrip gripped between heads 30 and 32.

The extent of stretch is determined by the mechanical .stops limitingthe stroke of piston 152 in cylinder 150. At the left end, the wall ofcylinder 50 forms a stop. At the right end, collar 154 limits thestroke. Collar 154 is adjustably screwed on the outside of cylinder 150and is externally uted for engagement by ball detent '156 secured toframe 108. Shaft 46 is provided with .a keyway 158 and is held againstrotation with respect '1o cylinder 150 by key 160. The latter is securedto a plug 162 within cylinder 150 by means of a screw 164 'the head ofwhich abuts collar 154. A compression coil :spring 166 reacts betweenpiston 152 and plug 162 to maintain screw 164 in contact with collar 154in all its positions of axial adjustment.

When hydraulic uid is admitted to cylinder 150 from line 168, piston 152is urged to the right extreme as limited by plug 162 which in turn isarrested by collar 154. Upon release of the hydraulic pressure in line168, piston 152 is restored by spring 166 to its left-hand posi- Collar154 is externally provided with a calibrated scale 170 (see FIG. 5) sothat extent of -stretch of the grid side rods can be accurately changedwithout trial-and-error procedure.

The structure for operating the second shaft 48, parallel to shaft 46,is identical with that shown in FIG. 3 and both are energized by acommon hydraulic supply.

For the purpose of heating the side rods electrically during thestretching operation, a controlled voltage is ,applied between heads 30and 32, and for this reason these two heads are electrically insulatedapart. The connection of shaft 46 to frame 108 includes nut 172 spacedfrom frame 108 by an insulating washer 174, and bushing 176 on theopposite side of frame 108 is spaced from the frame by an insulatingbushing 178. Bushing 176 is held against rotation in relation toinsulating bushing 178 by means of key 180 that extends into keyway 158.Nut 182 on threaded shaft 46 tightens bushings 176 and 178 against frame108', confined by nut 172. .Electrical lines 184 and 186 are connectedrespectively to heads 30 and 32 and are energized by an appropriateportion of secondary winding 188 of a transformer having a selector tapswitch 190. The primary 192. of this transformer is energized from theusual power supply line through a control relay 194, switch 196, and camswitch 198 the purpose of which is to time the start and duration ofheating of the side rods. When it is not desired to utilize thehot-stretch provision, switch 196 is opened and grids can then be madeaccording to the cold-stretch procedure. The hydraulic lines feedingcylinders 52 and 54 of heads 30 and 32 are of nonrnetallic materials anddo not short-circuit the hot-stretch electrical circuit.

Hydraulic system and timing chart From the foregoing, it will beapparent that the longitudinal travel of the first and second feed headsand of the cutting head are eiected by cams 74 and 98. The stretchinghead 32 travels with head 30, but is given an 8 augmentedexcursion bymeans of hydraulic mecha'- nism including 150. The jaws in the severalheads are all operated, for closing on the grid strip and for opening,by hydraulic mechanism including a cylinder carried by each of the headsand exible lines leading to them.

The complete hydraulic system `for the entire machine isdiagrammatically shown in FIG. 8. Cylinders 50, 52, 54 and 186 foroperating the jaws of heads 28, 30, 32 and 34 are alternately suppliedwith high-pressure fluid at opposite ends, and are connected foi returnof the low-pressure uid to the supply hy means of a series of two-wayvalves 189. High-pressure supply line 191 is connected to all of thesevalves, and it in turn is supplied fby pump 193 and pressure regulator195 which has a return line 197 to sump 199. Hydraulic motor 200 withits control valve 202 for operating the entire machine is also shown inthis diagram. Valves 189 are connected for return of low-pressure fluidthrough lines 204 and 206 to sump 199. A second regulator 208 isprovided for reducing the available hydraulic pressure to `a suitablelevel for operating the stretching mechanism, including hydrauliccylinder 150. This mechanism is spring-restored rather than restored byhydraulic pressure. For this reason a slightly different valve 210 isutilized for connecting cylinder 150 alternately for input fromregulator 208 and `for discharge to return line 206. Picker 27 ishydraulically operated from the high-pressure lines, as indicated, justas in the case of the jaws in the various heads.

Valves 189 are cam-operated as indicated in FIG. 1A. Plural cams 212 aresecured to shaft 214 which is rotated once for each grid cycle, in timewith cam-shafts 84 and 100. Cams are also provided on shaft 214 foroperating valve 210 of the stretching head, and for hot-stretch switch198 shown in FIG. 2. The cam-operated valve detail is naturally subjectto wide variation, but the relative timing among the several valves isof importance.

rIlhe timing of the various operations will -be understood from FIG. 13.While this figure is actually a cam chart it is a close approximation ofa timing chart as well. It will be seen from the top section of thechart that cam 74 has portions for causing a gradual uniform forward orfeeding stroke of the first and second feeding heads, and a fast returnstroke, the division being about 260 and 100 and the return strokes arespaced by 180. Between zero and and between 180 and 260 botth headsAmove in unison and in thesame direction. From the second and thirdsections of the diagram it is apparent that the jaws of both heads 28and 30 are in engagement with grid strip G during a part of thesecorncurrent feeding strokes of heads 28 and 30, and the jaws of onefeeding head grip the strip at other times. It therefore follows thatIthe grid strip will be smoothly advanced past the winding and formingdevices atvthe left of FIGS. l and 2, and uniform grids will beproduced, The lead, or the extent of feed in a grid cycle, is controlledby the extreme limits of cam 74 which is therefore termed the lead cam.

Cam 98, it will be seen from the fourth portion yof FIG. 13,incorporates a long, very gradual sloping portion and a relativelyabrupt return portion. IThis cam simply varies the feeding rate of thegrid strip that would be caused by cam 74, the abrupt portion serving toimpart a fast, long feeding stroke `during the winding of the looseturns. The remainder of the cycle of cam 98 modifies the feeding rate ofcam 74 during the winding of secured turns. Where this long portion ofcam 98 is straight, the pitch of the grids will be uniform from end toend. The spacing bre-tween the successive secured turns of the grid canbe varied from one end of the grid to the other (FIG. 7) by properlycurving cam 98. Therefore cam 98 is termed the pitch cam.

When the machine is tobe changed from operati-on on one type of grid -toproduction of another type, cam 74 need not be removed if the length ofthe'new grid is the same as the old one. Cam 98 need not be replaced if`7 the distribution of the secured turns' and the lengthY of theloose-turn zone are not changed.

Comparing the fourth and fifth sections of FIG. 13 it is apparent thatthe fast-feeding operation that occurs simultaneously with the windingof unsecured turns occurs previous to the stroke of loose-turn picker27. This is because the grid strip should advance to cutters 24 and 25before the loose turns are parted from the secured turns. Thereforeloose-turn picker 27 is lowered at a later time in the grid cycle, afterthe winding of a number of secured turns.

Comparing the third and sixth sections of FIG. 13 it can be seen thatthe jaws of stretching head 32 engage the grid strip shortly `after thejaws of head 34.1 grip the strip. Similarly the stretching-head jawsrelease the grid strip shortly before the strip is released by the jawsof head 30. The engagement and release of both jaws take place in theregion of 190 to 200 and 40 to 50, respectively. Comparison of theseventh section of FIG. 13 with the sixth section shows that thestretching operation, effected by cylinder 156, takes place after thejaws of streaching head 32 grip the strip and that the piston incylinder 150 is restored after the jaws of head 32 have released thegrid strip. The electrical heating of the side rods is lcommenced andcompleted after the grid strip is gripped by both the second feedinghead and the stretching head, and the heating is interrupted shortlyafter pressure is admitted to the stretching cylinders, as 150, afterwhich the strip is supported during cooling.

The loperation of cutting head 34 corresponds to that of the firstfeeding h-ead 28. The cutting head, positioned beyond the stretchinghead, is not in engagement with the grid strip during the initiallyeffective part of the stretching operation as `controlled by cylinder150. The cutolf head, however, acts to support the end of grid strip Gafter the previous grid is parted, so that the grid strip will not sagwhile the jaws of stretching head 32 close to grip the strip.

In FIGS. 9 to l2 there are shown several feed-jaw details whichcontribute signicantly to the excellence of the feeding mechanism. As isapparent from the foregoing, and especially in connection with theoverlap in the feeding strokes of the first and second heads, it isdesirable that there be no interruption in the smooth travel of the siderods past the forming devices. It is likewise desirable that the feedjaws in the first and second heads do not change the length of thoseside rods in firmly gripping them, for this would defeat the carefularrangement directed to uniform feeding. One fonrn of feed-jaw detail isshown in FIGS. l and 10 as comprising a blade 216 fixed to slide 112(compare with FIG. 4) and a pressure pad 218 having portions on oppositefaces of blade 216. Pad 218 is spring-loaded by compression spring 22hand button 222 to contact grid strip G in advance of blade 216 and tostrip the side-rods from blade 216 4during the return stroke of slide112. A positive-acting backup block 224 is secured to slide 114 belowgrid strip G. As previously mentioned in connection with the mechanismof FIG. 4, sli-des 112 and 114 are operated to precisely determinedend-points, so that blade 216 will penetrate the side rods R of gridstrip G to an accurate extent. The jaws of two successively `actingheads are shown, enlarged, in FIG. 11. These are illustrative of thefirst and second feeding heads and of the second feeding head and thestretching head. The surface of blade 216 is formed to cause essentiallytransverse plastic flow of the side-rod material, thereby causing noelongation of the rod. Similarly shaped blade 216' is arranged in thefollowing head to take a new bite into the side rod R, still withoutcausing elongation of the side rod. The blades have lateral surfacesthat are essentially perpendicular to the side-rods and embody a Ygroove between them for accommodating the lateral fiow of side-rodmaterial. l

An alternative form of feeding-jaw detail is shown 1n FIG. 12, wherein apositively operated blade 226, flanked by a pressure pad 228, offsets aportion of the side-rod material without foreshortenng or elongatingthat side rod. The lateral surfaces of blade 226 are essentiallyperpendicular to the grid strip. The pressure block of FIG. 11 ismodified in FIG. 12 to comprise positive-acting portions 230` and -aresilient stripping pad 232 between portions 230. This construction alsoaccommodates the later-al flow of side-rod material. The offset formedin the first feed jaw can be reliably used for feeding without furtherdeformation in the arrangement shown by having a narrow positive-actingblade 218 register with the forward edge of the previously formeddepression.

The foregoing specication includes a detailed description of anillustrative embodiment of the invention, this embodiment incorporatingseveral closely related features which coact to facilitate and improvethe manufacture of grids. However it will be recognized that theparticular embodiment is susceptible to a wide latitude of modicationand substitution and portions of it are separately useful in improvingsimilar machines. Therefore the following claims should be interpretedbroadly, within the spirit of the invention.

What we claim is:

l. In a machine of the type described including means for modifying astrip of material, a feeding mechanism for moving the strip of materialpast said modifying means according to a cyclic feed-rate schedule,comprising a pair of four-motion feeding heads operable to grip thestrip alternately, lead cam mechanism reciprocating said heads alongsaid strip in an alternating relationship through a predeterminedstroke, and additional cam mechanism operatively connected to said leadcam mechanism for cyclically modifying the feeding rate that wouldotherwise be effected by said lead cam.

2. ln a machine of the type described including means for modifying astrip of material, a feeding mechanism for moving the strip of materialpast said modifying means according to a cyclic feed-rate schedule, saidfeeding mechanism comprising a pair of four-motion feeding heads, a rstcam, a pair of spaced cam followers on said cam, one of said lfollowersbeing operatively connected to each of said feeding heads forreciprocating said feeding heads, and a second cam for cyclicallyadjusting said first-mentioned cam to modify the feeding rates thatwould normally be caused by said first cam.

3. A grid-making machine having devices for winding and securinggrid-lateral wire about one or more side rods, said machine including afirst feeding head and a second feeding head, means for operating eachof said first and second feeding heads in alternation in a fourmotionpath to grip and advance the strips past the winding and forming devicesto effect continuous feeding, a cutting head having grid strip engagingjaws, and means for actuating said cutting head in substantialsynchronisrn with the first feeding head to bring said jaws intoengagement with the formed grid strip for dividing the formed gridstrips into individual grids, the actuating means for said cutting headmaintaining said jaws in engagement with the formed grid strip duringthe return stroke of said second feeding head for supporting the gridstrip against deflection during the return stroke of said second feedinghead, said second feeding head being positioned between said firstfeeding head and said cutting head.

4. A grid-forming machine having forming devices for winding andsecuring grid-lateral wire about one or more side rods, said machineincluding a feeding mechanism having a four-motion feeding head, meansoperatively connected to said feeding head for reciprocating saidfeeding head in `a path parallel to the travel of the formed grid strip,and a stretching head carried by said feeding head, means for engagingsaid stretching head with the grid strip during feeding thereof by saidfeeding head whereby saidstretching head is reciprocable parallel to thetravel of the formed grid strip and means for recipro- 9 cating saidstretching head through a longer stroke than said feeding head duringfeeding for stretching the side rod material.

5. A grid-forming machine having rst and second four-motion feedingheads, forming devices for winding and securing grid-lateral wire aboutone or more side rods, said side rods being continuously advanced pastsaid forming devices by said feeding heads, and a four-motion stretchinghead located beyond said heads in the feeding direction and carried byone of said heads and means for cyclically operating said four-motionstretching head generally in the same sequence as one of said feedingheads and at a greater rate during its engagement with lthe formed gridstrip to stretch the side-rod material.

6. A grid-making machine comprising devices for winding and securinggrid-lateral wire about one or more side rods to form a strip of gridmaterial, a first and a second four-motion feeding head reciprocable todraw the grid strip continuously at predetermined rates past thegridforming devices, and a four-motion stretching head carried by saidsecond feeding head and means for reciproeating said stretching head ata rate relative to said second feeding head for stretching the gridstrip during engagement of the second feeding head and the stretchinghead with the grid strip.

7. Apparatus according to claim 6 wherein piston and hydraulic cylinderare operatively connected to said stretching head to effect relativetravel between said second feeding head and said stretching head.

8. A grid-making machine having devices for forming a helical grid aboutone or more side rods, said machine having a feeding mechanism includingfirst and second four-motion feeding heads reciprocable parallel to thetravel of the formed grid strip and each arranged to engage the gridstrip during the respective feeding strokes thereof, hydraulic actuatingmechanisms including flexible uid lines respectively connected to saidheads, a stretching head for engaging the grid strip during the feedingthereof by said second feeding head, and hydraulic actuating mechanismsincluding a flexible fluid line for causing the stretching head tooperate through a longer stroke than said second feeding head forstretching the side rods.

9. A grid-making machine comprising devices for winding and securinggrid-lateral wire about one or more side rods to form a strip of gridmaterial, first and second four-motion feeding heads reciprocable todraw the grid strip continuously at a cyclic rate schedule past saidgrid-forming devices, a four-motion stretching head carried by saidsecond feeding head, means for moving said stretching head away fromsaid second feeding head and through a prescribed stroke for stretchingthe gridstrip during engagement of the second feeding head and thestretching head with the grid strip, means electrically insulating saidstretching head from said feeding head, an electrical supply connectedto said second head and said stretching head for heating the portion ofthe grid strip gripped between the latter heads, and hydraulic mechanismincluding electrically non-conducting liuid supply lines for causing atleast one of said latter heads to grip said strip.

l0. A grid-making machine including devices for winding and securinghelical turns to one or more side rods with predetermined spacingbetween the turns controlled by the feed-rate of the side-rods past saiddevices, said machine having a pair of sequentially effectivefour-motion feeding heads for reliably feeding the side rods accordingto a predetermined rate schedule, the first head comprising jaws havingparallel surfaces with edges arranged to penetrate the side-rod materialsubstantially perpendicularly, said jaws incorporating a recess betweensaid edges for accommodating the transverse ow of siderod material, anda pair `of jaws in the second head for engaging the side rods inregistry with the zone previously penetrated.

ll. A machine adapted to modify strip material passed through saidmachine, and including means past .which said strip progresses and whereoperations are performed upon said material, a first and a secondgripping head', means operatively connected to said first and secondgripping heads to alternately reciprocate said heads back and forthalong the path of travel of said strip material, each of said headshaving jaws to engage said strip ma: terial, means to alternatelyoperate said jaws to continuously draw said material through saidmachine, and a stretching head carried by the second of said heads;means for mounting said stretching head for movement relative to saidsecond head, said stretching head having jaws to engage said material,meansto engage the jaws of said stretching head when the jaws carried bysaid second head are closed, and means for increasing the spacingbetween said second head and said stretching'. head, while the jawscarried by said heads are closed whereby said material is stretched.

l2. A machine having strip material feeding means in'- cluding a pair ofsequentially effective four-motion feeding heads reciprocable along theline of travel of said material through said machine, the first of saidheads having material clamping jaws with parallel surfacesand edgesarranged to penetrate said material perpendicularly, and a recessbetween said edges for accommodating transverse flow of said material,the second of said heads including material clamping jaws with parallelsurfaces and edges arranged to penetrate said materiai perpendicularly`at each side of the points of penetration of said first jaws, the flowof material caused by the clamping yof said second jaws taking placeinto the depressions formed by said rst jaws without causing a change oflength of said strip material.

13. A grid making machine comprising devices for winding and securinggrid lateral wire about one or more side rods to form a strip of gridmaterial, first and second four-motion feeding heads, means foralternately reciprocating said feeding heads to draw said grid stripmaterial continuously at a cyclic rate schedule past said grid formingdevices, a four-motion stretching head carried by said second feedinghead and having gripping means yarranged to clamp said grid stripsimultaneously with said second head, means for engaging said grippingmeans during feeding by said second head, means for reciprocating saidstretching head relative to said second head whereby said grid strip isstretched, a cutting head beyond said stretching head and carried bysaid first head, and means to operate said cutting head to engage saidstrip simultaneously with said first head to sever the portion of saidgrid material beyond said cutting head and to support the grid stripbetween said first feed head and said cutting head.

14. A machine of the type described including means for modifying lastrip of material, and a feeding mechanism for moving the strip ofmaterial past said modifying means accord-ing to a cyclic feed rateschedule, comprising a pair of feeding heads disposed one after theother along the path of travel of said strip of material, lead cammechanism for reciprocating said heads along said strip in analternating relationship through a predetermined stroke, clamping jawson each head, means operatively connected to the respective jaws toclose the jaws at one end of each stroke and to open the jaws at theother end of said stroke, and additional cam mech-anism operating onsaid lead cam mechanism for cyclically modifying the rate of travel ofsaid heads.

l5. A machine of the type described including means for modifying astrip of material, and a feeding mechanism for moving the strip ofmaterial past said modifying means according to a cyclic feed rateschedule, comprising a pair of feeding heads disposed one after theother along the path of travel of said strip of material, a cam followerfor each of said feeding heads, a lead cam ,engaging said cam followersfor reciprocating said heads along said strip in an alternatingrelationship through a predetermined stroke, clamping jaws on each head,means operatively connected to the respective jaws to close the jaws atone end of each stroke and to open the jaws at the other end of saidstroke, and additional cam mechanism operating on said lead cam forcyclically modifying the rate of travel of said heads, said camfollowers being mutually spaced about said lead cam.

16. A machine of the type described including means for modifying astrip of material, and a feeding mechanism for drawing a strip ofmaterial cyclically past said operating means according to apredetermined feed rate schedule, said feeding mechanism comprising apair of feeding heads disposed one after the other along the path oftravel of said strip of material, each feeding head having a camfollower for reciprocating it along the path of the strip and lead cammechanism having a cylindrical cam engaging said cam followers forreciprocating said heads along said strip in an alternating relationshipthrough a predetermined stroke, clamping jaws on each head, meansoperatively connected to the respective jaws to close the jaws at oneend of each stroke and to open the jaws at the other end, and additionalcam mechanism operating on said lead cam for cycl-ically modifying therate of travel of said heads.

17. A machine of the type described including means for modifying astrip of material, and a feeding mechanism for moving the strip ofmaterial past said modifying means according to a cyclic feed rateschedule, comprising a pair of feeding heads disposed one after theother along the path of travel of said strip of material, lead cammechanism for reciprocatingV said heads along said strip in analternating relationship through a predetermined stroke, clamping jawson each'head operated to close at one end of each stroke and to open atthe other end of said stroke, and additional cam mechanism operating onsaid lead cam mechanism for cyclically modifying the rate of travel ofsaid heads, one of said heads carrying a set of stretching clamp jaws,means for cyclically causing said stretching jaws to grip said stripwhile the clamping jaws on said one head are closed, and means formoving said stretching jaws with relation to the clamping jaws on saidone head to stretch said strip of material.

18. A machine of the type described including means for modifying astrip of material, and a feeding mechanism for moving the strip ofmaterial past said modifying means according to a cyclic feed rateschedule, comprising a pair of feeding heads disposed one after theother along the path of travel of said strip of material,

each feeding head having a cam follower associated i therewith, a leadcam engaging said cam followers for reciprocating said heads along saidstrip in an alternating relationship through a predetermined stroke,clamping jaws on each head operated to close at one end of each strokeand to open at the other end of said stroke, and

additional cam mechanism operating on said lead cam for cyclicallymodifying the rate of travel of said heads7 said cam followers beingmutually spaced about said lead cam, one of said heads carrying a set ofstretching clamp jaws, means for cyclically causing said stretching jawsto grip said strip while the clamping jaws on said one head are closed,and means for moving said stretching jaws with relation to the clampingjaws on said one head to stretch said strip of material.

19. A grid forming machine having rst and second feeding heads disposedone after the other along the path of travel of said grid, clamping jawson each head, means connected to said clamping jaws to close at one endof each stroke and to open at the other end, forming devices for windingand securing grid lateral wire about one or more side rods, means forreciprocating said feeding heads such that said side rods arecontinuously advanced past said forming devices by the alternatereciprocating 'action -of said feeding heads, and a stretching headlocated beyond said heads in the feedingdirection and carried by one ofsaid heads and including clamping jaws, means for cyclically operatingsaid clamping jaws of said stretching head in the same sequence as thejaws of one of said feeding heads, and means for moving said clampingjaws of said stretching head with respect to said one of said feedingheads.

20. A machine of the type described including means for modifying astrip of material, and a feeding mechanism for moving the strip ofmaterial past said modifying means according to a cyclic feed rateschedule, comprising a pair of feeding heads disposed one after theother along the path of travel of said strip of material, cam mechanismfor reciprocating said heads along said strip in an alternatingreltaionship through a predetermined stroke, clamping jaws on each head,means operatively connected to the jaws on the respective heads to closethe jaws at one end of each stroke and to open the jaws at the other endof said stroke, said jaws having lateral surfaces substantiallytransverse of said strip of material and incorporating a recess betweensaid surfaces for accommodating transverse flow of said material.

2l. A machine of the type described including means for modifying astripof material, and a feeding mechanism for moving the strip of materialpast said modifying means according to a cyclic feed rate schedule,comprising a pair of. feeding heads disposed one after the other alongthe path of travel of said strip of material, cam mechanism forreciprocating said heads along said strip in an alternating relationshipthrough a predetermined stroke, clamping jaws on each head, meansoperatively connected to the jaws on the respective heads to close thejaws at one end of each stroke and to open the jaws at the other end ofsaid stroke, the jaws of the r trst of said heads including a blade fordeforming the strip of material laterally while maintaining its lengthconstant, and the second of said heads having jaws registering with thedeformation previously affected by jaws of said rst head.

22. A machine of the type described including means for modifying astrip of material, and a feeding mechanism for moving the strip ofmaterial past said modifying means according to a cyclic feed rateschedule, comprising a pair offeeding heads disposed one after the otheralong the path of travel of said strip of material, cam mechanism forreciprocating said heads along said strip in an alternating relationshipthrough a predetermined stroke, clamping jaws on each head, meansoperatively connected to the jaws on the respective heads to close thejaws at one end of each stroke and to open the jaws at the other end ofsaid stroke, the jaws of the first of said heads having parallelsurfaces with edges arranged to penetrate a strip of materialsubstantially perpendicularly of the length of said strip, said jawsincorporating a recess between said edges for accommodating transverseow of said material, and the jaws in the second of said heads engagingthe strip of material in registry with the zone previously penetrated bythe jaws of said first head.

23. A machine of the type described including means for modifying astrip of material, and a feeding mechanism for moving the-strip ofmaterial past said modifying means according to a cyclic feed rateschedule, comprising a pair of feeding heads disposed one after theother along the path of travel of said strip of material, cam mechanismfor reciprocating said heads along said strip in an alternatingrelationship through a predetermined stroke, clamping jaws on each headoperated to close at one end of each stroke and to open at the otherendof said stroke, the clamping jaws on each head including a blademounted transversely of the strip of material gripped thereby, the bladeof the clamping jaws of the rst of said heads acting to ofset a portionof the strip of material gripped thereby and the blade in the clampingjaws of the second of said heads being adjusted i3 to clamp said stripof material in the offset formed by the blade in the first of saidheads, the blade in the second of said heads being narrower than theblade in the first of said heads to prevent the clamping operation frommodifying the length of said strip of material.

24. A machine of the type described including means for modifying astrip of material, and a feeding mechanism for moving the strip ofmaterial past said modifying means according to a cyclic feed rateschedule, comprising a pair of feeding heads disposed one after theother along the path of travel of said strip of material, lead cammechanism for reciprocating said heads along said strip in analternating relationship through a predetermined stroke, clamping jawson each head operated to close at one end of each stroke and to open atthe other end of said stroke, one of said heads carrying a set ofstretching clamp jaws, means for cyclically causing said stretching jawsto grip said strip while the clamping jaws on said one head are closed,and means for moving said stretching jaws with relation to the clampingjaws on s aid one head to stretch said strip of material.

25. A machine of the type described including means for modifying astrip of material, and a feeding mechanism for moving the strip ofmaterial past said modifying means according to a cyclic feed rateschedule, comprising a pair of feeding heads disposed one after theother along the path of travel of said strip of material, lead cammechanism for reciprocating said heads along said strip in analternating relationship through a predetermined stroke, clamping jawson each head, means operatively connected to the jaws on the respectiveheads to close the jaws at one end of each stroke and to open the jawsat the other end of said stroke, one of said heads carrying a set ofstretching clamp jaws, means for cyclically causing said stretching jawsto grip said strip while the clamping jaws on said one head are closed,and means for moving said stretching jaws with relation to the clampingjaws on said one head to stretch said strip of material, means forinsulating said stretching clamp jaws from the one of said headscarrying said stretching clamp jaws and means for applying an electricalpotential differvence between said one of said heads and said stretchingclamp jaws.

26. In a machine having a feeding mechanism operable for moving a stripof material through said machine, said feeding mechanism including apair of heads each having material gripping jaws constructed andarranged to firmly grip said material in succession at the same point,the first one of said gripping jaws being recessed whereby a portion ofsaid material strip is deformed into said recess, the second one o-fsaid jaws being arranged to engage said strip of material at each sideof the zone 4of engagement of the first jaws.

parting stretch to said side rods, and means for moving said stretchingdevice with said gripping means engaging said side rods along said pathat a rate in excess of said predetermined feed rate, whereby astretching and straightening action is exerted on said side rods.

28. In a grid-forming machine, means for performing an operation on agrid, and a feeding mechanism for moving said grid according to a cyclicfeed-rate schedule, said feeding mechanism including a pair offour-motion feeding heads, a first cam, a pair of cam followers engagingsaid cam, one of said followers being operatively connected to each ofsaid feeding heads for reciprocating id said feeding heads, a secondcam, and a cam follower engaging said second cam and operativelyconnected lto said first cam for cyclically shifting said first cam.

29. In a grid-making machine, means for Winding and securinggrid-lateral wire about one or more side rods in a grid strip, a firstfeeding head, a second feeding head, means for moving each of saidfeeding heads in a fourmotion feed path having a forward stroke forgripping and advancing said grid strip and a return stroke, means formoving said feeding heads in alternation to effect continuous feeding, acutting head, means for operating said cutting head in substantialsynchronism with said first feeding head for dividing said grid stripinto individual grids, said cutting head being operative to support saidgrid strip against deflection during the return stroke of said secondfeeding head.

30. A grid-forming machine including means for modifying -a strip ofmaterial, and a feed mechanism for moving the strip of material pastsaid modified means according to a cyclic feed rate schedule, saidfeeding mechanism comprising a pair of heads disposed along the path oftravel of said strip of material, mechanisms for moving said heads alongsaid path of travel in alternate relationship and through apredetermined stroke, feeding clamp jaws on each of said heads arrangedto close at a predeteilmined point along said stroke, a set ofstretching clamp jaws, means for mounting said stretching clamp jaws onone of said heads for normal movement therewith and for movementrelative thereto, means for 4cyclically causing said stretching clampjaws to grip said strip while said feeding clamp jaws on said one headare closed, and means for moving said streching clamp jaws with relationto said feeding clamp jaws on said one head to stretch said strip ofmaterial.

3l. A grid-forming machine including -means for modifying a strip ofmaterial, and a feed mechanism for moving the strip of material pastsaid modifying means according to ya cyclic feed rate schedule, saidfeed mechanism comprising a pair of heads disposed along a path oftravel of said strip of material, feeding clamp jaws on each of said.feed heads operated to periodically close `for gripping said strip ofmaterial, one of the feeding clamp jaws of the first of said headshaving a notch therein transverse of said strip of material, said one ofthe feeding clamp jaws of the first of said heads acting in clamping toprovide notches transverse to the length of said strip of material, thevfeeding clamp jaws of the second of said heads having a notch thereintransverse to the length of said strip of material, said notch beingbroader than the notch in said first named feeding clamp jaws wherebythe feeding clamp jaws of the second of said heads in clamping on saidstrip of material deforms the material of said strip into the notchesformed by the first named lfeeding c-lamp jaws.

32. `In a grid-making machine, means along a predetermined path formodifying a grid strip, and feeding mechansms operative along saidpredetermined path for moving said grid strip past said modifying meansaccording to a cyclic feed-rate schedule, said feeding mechanismsincluding first and second heads each mounted for reciprocating movementalong said predetermined path, stripengaging means on each of saidheads, means operative at selected intervals in said feed-rate schedulefor moving said strip-engaging means into gripping engagement with saidgrid strip, a first cam, first and second cam followers under control ofsaid first cam, means connecting said first follower to said first head,means connecting said second follower to said second head, and meansincluding a second cam operatively connected to said first cam forcyclically adjusting said first cam in relation to said first Iandsecond cam followers to modify the feeding rates of said first andsecond heads as normally determined by said first cam.

33. In a grid-making machine, means along a predetermined path formodifying a grid strip, and Ifeeding mechanisms operative along saidpredetermined 4path for movf ing said grid strip past said modifyingmeans according to a cyclic feed-rate schedule, said feeding mechanismsincluding first and second heads each' mounted for reciproeating`movement along said predeter-mined path,vstrip engaging jaws on each ofsaid heads, means operative at selec-ted intervals -for moving said jawstoward each other and into engagement with said grid strip, a first cam,first and second cam fol-lowers mutually spaced about and under controlof said rst cam, means connecting said first follower to said firsthead, means vconnecting said second follower to said second head, saidfirst cam and said first and second cam followers being arranged to time4the reciprocation of said first and second heads whereby during thereturn stroke of one head, the other head is driven through its feedstroke, and means -Yincluding a second cam operatively connected tojsaidfirst cam for axially shifting said first cam to modify the feedingrates of said first and second heads as normally determined bysaidfirstcam. ,l

34. In a grid-making machine, means lalong a predetermined path forwinding and securinga grid lateral about side rods in a grid strip,feeding mechanisms operative along said predetermined path for movingsaid grid strip past the winding and securing means according to acyclic feed-rate schedule, said feeding mechanisms including iinst'andsecond feeding lheads each mounted for reciprocating movement inalternation along' sa-id predetermined path, strip-engaging jaws on eacho-f said feeding heads, meansoperative during the forward feeding strokeof the respective feeding heads for closing said jaws into engagementwith said grid strip, respective drive means operatively connected tosaid rst and second feeding heads for moving said first and second-feeding heads in alternation, a cutting head'operatively connected tosaid rst feeding head for reciprocation therewith; cuttingV jaws on saidcutting head, means operative -in substantial synch'ronism with theclosing of the jaws of said first .feeding head lfor closing saidcutting jaws on said grid strip toV divide said grid strip intoindividual grids, said cutting jaws remaning closed during the returnYstroke of said second feeding heads to support said grid strip againstdeflection, a stretching head operatively connected to said secondfeeding head for reciprocation therewith, stretching jaws on saidstretching head, means operative insubstantial synchronism with theclosing of the jaws of said second feeding head for closing saidstretching jaws on said grid strip, and means operatively connected tosaid stretching head for -moving said stretching head away from saidsecond feeding head during the forward feeding stroke of said secondfeeding head.

35. A grid-forming machine including means `along a predetermined pathfor modifying a strip of material, and a feed mechanism for moving saidstrip past said modied means according to a cyclic feed rate schedule,said feeding mechanism comprising a pair of feeding heads disposed alongthe path of travel of saidV strip, driving mechanisms for moving saidfeeding heads along said path of travel in alternate relationship,strip-engaging means on each of said feed-ing heads arranged to close onsaid strip, a stretching head operatively connected to one of said`feeding heads, strip-engaging means on said stretching head arranged toclose on saidv strip, means for closing the strip-engaging means of saidstretching head on said strip while said strip-engaging means on saidone feeding head is closed on said strip, and means `for moving saidstretching head through a longer stroke than said onepfeeding headwhilevthearespective strip-engaging means are closed to stretch saidstrip of material. Y Y

36. In a grid-making machine, means along Aa predetermined path Vformodifying a grid strip of the type including side rods and a gridlateral wound about said side rod's`,"and feeding mechanisms includingat least one head operative along Said 'predeterminedlvpathfor movingsaid grid strip past said modifying means according toa cyclic feedarateschedule, strip-engaging jaws on said head movable into engagement alongthe length of said Vside rods of said grid strip, said strip-engagingjaws being coustructed and arranged to cause transverse flow of thematerial of said side rods within the limits of said strip-en.- gagingjaws whereby said side rods are reliably gripped without elongation ofsaid side rods, said strip-engaging jaws havingv lateral surfacesextending substantially transverse `of said side rods, there being arecess formed between said lateral surfaces for accommodating saidtransverse liow of the material of said side rods.

`3,7. In a grid-making machine, means along a predetermined path formodifying a grid strip of the type including side rods and -a gridlateral wound about said side rods, and feeding mechanisms operativealong said predetermined path for moving said grid strip past saidmodifying means according toa cyclic feed-rate schedule, said feedingmechanism including .first and second heads each mounted forreciprocating movement along said predetermined path, strip-engagingmeans on each of said heads movable into engagement along the length ofsaid side rods of said gri-d strip, the respective strip-engaging meansbeing constructed and arranged to defor'm saidside rods and to causetransverse flow of the material of said side rods within the limits ofthe strip-engaging means whereby said side rods are reliably grippedwithout elongation of said rods, the strip-engaging'means on said firsthead including a blade deforming thermaterial of the side rodslaterally, the strip-engaging means on said secondhead including jawsregistering with the deformation caused by said blade. v a

38. In a machine for modifying a strip of material passing along a pathof travel through said machine, means along said path for performingoperations on said strip, first and second gripping heads,meansoperatively connected to said gripping heads for alternatelyreciprocating said gripping heads backv and forth'alon'g said path,movable jaws on each of said gripping heads for gripping said strip,means operatively connectedy to said jaws for alternatelyoperating saidjaws to continuously draw said strip through said machine, a stretchinghead carried `by said second gripping head, means mounting saidstretching head for movement relative to said'second gripping head,movable jaws on said stretching head, means operatively connected to thejaws of said gripping'he'ad for closing same when the jaws of saidsecond gripping head are closed, means operatively connected betweensaid second gripping head and said stretching head for increasing thespacing between said second gripping head and said stretching head whenthe jaws on the respectiveheads are closedwhereby said strip'isstretched, and means for passing a current through said 4strip duringstretching, the jaws of each of said heads being constructed and formedto grip said strip without changing the length of said strip.

39. In a machine for modifying a strip of material passing along a pathof travel through said machine, means along said path for performingoperations on said strip, first and second gripping heads,meansoperatively connected to said gripping heads 'for alternatelyreciprocating said gripping heads back and forth along said path,movable jaws on each of said gripping heads for gripping said strip,means operatively connected to said jaws for alternately operating saidjaws to continuously draw said strip through said machine, a stretchingIhead carried by said second gripping head, means mounting saidstretching head for movement relative to said second gripping head,movable jaws on saidstretching head, means operatively connected to thejaws of said gripping head for closing same when the jaws of said secondgrippinghead are closed, means operatively connected between .saidsecond gripping head rand said stretching 'head 4for increasing thespacing between said second gripping head and said stretching head whenthe jaws on the respective 17 heads are closed whereby said strip isstretched, and means for heating said strip as said strip is stretched.

40. A machine comprising strip material feeding mechanisms includingfirst and second feeding heads each mounted for reciprocating movementalong the line of travel of said strip material through said machine,each of said feeding heads including a movable jaw having a bladeprovided with lateral surfaces substantially per pendicular to said lineof travel and pressure pads ilanking said blade and abutting saidlateral surfaces, and a fixed jaw including a back-up member cooperatingwith said pressure pads and a spring-mounted stripper member depressibleto accommodate lateral ow of said strip material, the blade of saidsecond feeding head being arranged to register in the depression formedin said strip material by 4the blade of said first feeding head.

41. A machine comprising strip material feeding mechanisms includingsequentially effective first and second feeding heads each mounted forreciprocating movement along the line of travel of said strip materialthrough said machine, each of said feeding heads including a movable jawhaving a blade provided with lateral surfaces substantiallyperpendicular to said line of travel and edges arranged to penetratesaid strip material, said blade being formed with a recess between saidedges for accommodating transverse flow of said strip material, pressurepads flanking said blade and abutting said lateral surfaces, and a fixedjaw including a back-up member cooperating with said movable jaw, theedges of the 18 blade of said second feeding head being arranged topenetrate said strip material at points outwardly of the points ofpenetration of the edges of the blade of said rst feeding head wherebythe transverse ow of strip material brought about by gripping of saidsecond feeding head takes place into depressions formed by said firstfeeding head.

42. In a grid-making machine, means along a predetermined path formodifying a grid strip, feeding mechanisms operative along saidpredetermined path for moving said grid strip past said modifying meansaccording to a cyclic feed-rate schedule, rotary lead cam means in anormal operative position, driving connection including cam followersbetween said lead cam means and said feeding mechanisms for mo'ving saidfeeding mechanisms, means for mounting said rotary lead cam means formovement relative to said normal operative position, additional cammeans, and additional driving connections between said lead cam meansand said additional cam means whereby said additional cam means shiftssaid lead cam means for cyclically modifying the feed rate that wouldotherwise be affected by said lead cam means,

References Cited in the file of this patent UNITED STATES PATENTS

